Monday, November 5, 2007 : 12:30 p.m.

Site Assessment Using Laser Induced Fluorescence (LIF) at Hydrocarbon Contaminated Sites

Jason Kirwin and Joann Dyson, Ph.D., West Central Environmental Consultants Inc.

The value of real-time, in-situ site characterization is being recognized, changing the way hydrocarbon investigations are performed.  The in-situ method of laser-induced fluorescence (LIF) detects fluorescence produced by polycyclic aromatic hydrocarbons (and thus NAPL) when excited by down-hole laser light.  This technology allows for continuous vertical assessment of NAPL (free and residual) and identification of the NAPL smear zone.  In addition, differentiation between lighter and heavier fuels is possible.  This makes LIF a valuable tool for tasks such as source identification or remediation planning.


Two distinct case studies will be presented, one where LIF was utilized primarily as an investigative tool, and a second where LIF was used primarily as a remedial tool.  The LIF technology utilized in these investigations is the UltraViolet Optical Screening Tool (UVOST™).  In the investigative study, the UVOST™ LIF revealed that released product initially migrated downward via gravity flow within the subsurface.  Hydraulic conductivity variations in the subsurface directed the release offsite prior to impacting the underlying aquifer, where advection-influenced migration pulled contamination to a municipal well.  In the remedial study, the extent of soil and groundwater contamination had been previously defined via laboratory analyses.  The UVOST™ LIF was utilized to define the horizontal and vertical extent of the NAPL plume, which was determined to be 80% below the water table.

Jason Kirwin, West Central Environmental Consultants Inc. Mr. Kirwin is a project manager at WCEC. He has a BA in biology and has over 16 years of experience in the environmental investigation and consulting field. Mr. Kirwin is also a member of the Minnesota Department of Homeland Security and Emergency Management’s regional Chemical Assessment Team (CAT). In addition, he is a registered Minnesota Department of Health Monitoring Well Contractor, an MPCA certified ISTS Designer/Inspector (#1296), and a BWSR certified wetland delineator.

Joann Dyson, Ph.D., West Central Environmental Consultants Inc. Ms. Dyson is a project manager at WCEC and has over 7 years of experience in the environmental investigation and consulting field. Ms. Dyson also has a Ph.D. in physics and over 6 years of experience in the field of laser spectroscopy. In addition, she is a member of the Minnesota Department of Homeland Security and Emergency Management’s regional Chemical Assessment Team (CAT).


Petroleum Hydrocarbons and Organic Chemicals in Ground Water: Prevention, Detection, and Remediation® Conference